Not Applicable
1. Field of the Invention
The present invention relates to a method for processing a striking plate for a golf club head. More specifically, the present invention relates to a method for chemical etching a forged metal striking plate for a golf club head to achieve proper thickness uniformly.
2. Description of the Related Art
When a golf club head strikes a golf ball, large impacts are produced that load the club head face and the golf ball. Most of the energy is transferred from the head to the golf ball, however, some energy is lost as a result of the collision. The golf ball is typically composed of polymer cover materials (such as ionomers) surrounding a rubber-like core. These softer polymer materials having damping (loss) properties that are strain and strain rate dependent which are on the order of 10-100 times larger than the damping properties of a metallic club face. Thus, during impact most of the energy is lost as a result of the high stresses and deformations of the golf ball (0.001 to 0.20 inches), as opposed to the small deformations of the metallic club face (0.025 to 0.050 inches). A more efficient energy transfer from the club head to the golf ball could lead to greater flight distances of the golf ball.
The generally accepted approach has been to increase the stiffness of the club head face to reduce metal or club head deformations. However, this leads to greater deformations in the golf ball, and thus increases in the energy transfer problem.
Some have recognized the problem and disclosed possible solutions. An example is Lu, U.S. Pat. No. 5,499,814, for a Hollow Club Head With Deflecting Insert Face Plate, discloses a reinforcing element composed of a plastic or aluminum alloy that allows for minor deflecting of the face plate which has a thickness ranging from 0.01 to 0.30 inches for a variety of materials including stainless steel, titanium, KEVLAR(copyright), and the like. Yet another Campau invention, U.S. Pat. No. 3,989,248, for a Golf Club Having Insert Capable Of Elastic Flexing, discloses a wood club composed of wood with a metal insert.
Although not intended for flexing of the face plate, Viste, U.S. Pat. No. 5,282,624 discloses a golf club head having a face plate composed of a forged stainless steel material and having a thickness of 3 mm. Anderson, U.S. Pat. No. 5,344,140, for a Golf Club Head And Method Of Forming Same, also discloses use of a forged material for the face plate. The face plate of Anderson may be composed of several forged materials including steel, copper and titanium. The forged plate has a uniform thickness of between 0.090 and 0.130 inches.
Another invention directed toward forged materials in a club head is Su et al., U.S. Pat. No. 5,776,011 for a Golf Club Head. Su discloses a club head composed of three pieces with each piece composed of a forged material. The main objective of Su is to produce a club head with greater loft angle accuracy and reduce structural weaknesses.
The typical forging process for metal golf club faces involves heating the metal bar at a temperature in excess of 1000xc2x0 C. for longer than twenty minutes, pressing and then repeating the process. The forged face is then milled or ground to obtain the proper face thickness. Thus, all current golf club forged face plates undergo a post-forging milling or grinding step to achieve a proper thickness, and proper bulge and roll. However, this milling and grinding of forged face plate cannot achieve a uniform reduction in thickness.
The present invention provides a method for chemically etching a forged face member for golf club head to achieve a relatively thin striking plate in a uniform manner. The thin striking plate allows for greater compliance of the striking plate with a golf ball during impact. A more compliant striking plate provides for lower energy loss and a higher coefficient of restitution.
One aspect of the present invention is a method for chemically etching a finished forged striking plate for a golf club head. The method includes forging a face member with a striking plate to a final configuration having predetermined thickness. Next, the forged face member with the striking plate is chemically etched in an acidic bath to uniformly remove 0.002 inch to 0.015 inch from the forged face member with the striking plate. Preferably, 0.003 inch each surface of the forged face member with the striking plate.
The forging process may include heating a metal bar to a temperature less than 1000xc2x0 C. for less than 20 minutes, and then pressing the heated metal bar into an L-shape metal bar. Next, the L-shape metal bar is again heated to a temperature less than 1000xc2x0 C. for less than 20 minutes, and then pressed into an intermediate shape face member. Next, the intermediate shape face member is coated with a glazing compound. Next, the coated intermediate shape face member is heated to a temperature less than 1000xc2x0 C. for less than 20 minutes, and then pressed into a final face member configuration.
The method may also include additional heating and pressing at even lower temperatures and at a lowered pressure to finalize the bulge and roll of a striking plate of the final face member configuration. The preferred metal is titanium, and most preferably alpha-beta-titanium. The multiple heating and pressing provides a thin face with greater durability.